Methods and systems for measuring optical properties of transistor channel structures and linking the optical properties to the state of strain are presented herein. Optical scatterometry measurements of strain are performed on metrology targets that closely mimic partially manufactured, real device structures. In one aspect, optical scatterometry is employed to measure uniaxial strain in a semiconductor channel based on differences in measured spectra along and across the semiconductor channel. In a further aspect, the effect of strain on measured spectra is decorrelated from other contributors, such as the geometry and material properties of structures captured in the measurement. In another aspect, measurements are performed on a metrology target pair including a strained metrology target and a corresponding unstrained metrology target to resolve the geometry of the metrology target under measurement and to provide a reference for the estimation of the absolute value of strain.
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2. The metrology target pair of claim 1, wherein the real transistor device structure is a Fin Field Effect Transistor (FINFET) devices.
3. The metrology target pair of claim 1, wherein each of the unstrained metrology target structures of the second periodic array include a channel structure without an epitaxial source structure and an epitaxial drain structure fabricated at either end of the channel structure.
4. The metrology target pair of claim 1, wherein each of the unstrained metrology target structures of the second periodic array include an epitaxial source structure and an epitaxial drain structure at either end of the channel structure fabricated from the same material as the channel structure.
5. The metrology target pair of claim 1, wherein the channel structure of each of the strained metrology target structures of the first periodic array is fabricated with Silicon.
6. The metrology target pair of claim 5, wherein the source and drain structures of each of the strained metrology target structures of the first periodic array is fabricated with Silicon doped with Germanium, Phosphorous, Carbide, or any combination thereof.
7. The metrology target pair of claim 5, wherein the channel structure of each of the unstrained metrology target structures of the second periodic array is fabricated with Silicon doped with Germanium, Phosphorous, Carbide, or any combination thereof.
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June 3, 2021
February 7, 2023
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